egress

egress example

Important

PREVIEW ONLY This package is provided as a preview for feedback only. APIs are unstable and the design is subject to change.

This Worker sends one URL through all three Cloudflare Computer execution backends:

• the container shell runs curl;
• the Worker shell runs its curl command;
• Worker JavaScript runs fetch.

EGRESS_MODE applies the same egress policy to every backend.

EGRESS_MODE	Workspace policy	Behavior
none	{ mode: "none" }	Blocks outbound network access. This is the default.
all	{ mode: "direct" }	Allows direct outbound access.
custom	{ mode: "http-gateway" }	Routes requests through a gateway that allows only https://example.com. Other origins receive 403.

Run it

The container backend requires Docker. Start the example with one of the three modes:

npm run dev --workspace @example/computer-egress -- --var EGRESS_MODE:none
npm run dev --workspace @example/computer-egress -- --var EGRESS_MODE:all
npm run dev --workspace @example/computer-egress -- --var EGRESS_MODE:custom

Then send a request:

curl -X POST 'http://127.0.0.1:8787/fetch?url=https%3A%2F%2Fexample.com'

The endpoint returns the status code and MIME type from each backend, or an error when no response was available:

{
  "mode": "all",
  "url": "https://example.com/",
  "container": { "status": 200, "mimeType": "text/html" },
  "worker-shell": { "status": 200, "mimeType": "text/html" },
  "worker-javascript": { "status": 200, "mimeType": "text/html" }
}

With EGRESS_MODE=none, each backend returns an error object. With EGRESS_MODE=custom, try an origin outside the allowlist to see the gateway response:

curl -X POST 'http://127.0.0.1:8787/fetch?url=https%3A%2F%2Fcloudflare.com'

Each backend reports status 403 and MIME type text/plain.

HTTP surface

POST /fetch?url=<HTTP-or-HTTPS-URL>

The endpoint accepts only POST. Missing, malformed, and non-HTTP URLs return 400.

Layout

examples/egress/
  Dockerfile                computerd, FUSE libraries, and curl
  wrangler.jsonc            Worker Loader, container, durable object, and EGRESS_MODE
  src/egress.ts             egress policy and response helpers
  src/index.ts              gateway, three backends, and HTTP handler